US Patent 9747171 Point-in-time copy restore

Managing storage volumes in a point-in-time copy cascade. The cascade includes a first source volume, a first target volume and a second target volume. The method detects a corruption of the first source volume and, if a first restoration of the first source volume from the first target volume is in progress, creates a third target volume from the second target volume and directs I/O operations for the first source volume to the third target volume. The first restoration is stopped. The first source volume is restored from the third target volume, and the third target volume is deleted.